The purpose of the study is to examine child, adolescent, and adult understanding and adaptation to severe illness and treatment that involves participation in human experiments. Patients' understanding of human experimentation, through the process of informed consent, provides an arena for studying reasoning and responses related to highly stressful life events. Participants will include child, adolescent, and adult in-patients and normal volunteers at the National Institutes of Health. Methods will include interviews, systematic observations, standardized psychological tests, psychophysiological measurements, and adrenal hormone measurements. Participants will be assessed during their initial admission to the Clinical Center and three and six months later.